/**
 * 获取用户Token
 */
export function getToken(ctx) {
  const header = ctx.request.header.authorization

  if (!header) {
    return null
  }

  const parts = header.split(' ')
  if (parts.length !== 2) {
    return null
  }

  const scheme = parts[0]
  const token  = parts[1]
  
  if (/^Bearer$/i.test(scheme)) {
    return token
  }

  return null
}